The Black Hawk helicopter which collided with a passenger plane above Washington DC was training for a hypothetical doomsday scenario at the time, according to US officials.
Three soldiers inside the military aircraft were killed as well as 64 people aboard the American Airlines jet.
The scenario involved practising the evacuation of high-ranking US officials, Reuters reported.
An investigation into the cause of the catastrophe is ongoing.
A Coast Guard vessel with a crane works near the helicopter wreckage in the Potomac River. Pic: AP
It has emerged that the helicopter had been on a training flight along a route core to a seldom-discussed military mission – to evacuate senior officials to safety in the event of an attack on the US, officials say.
The mission is known as “continuity of government” and “continuity of operations” and is meant to preserve the ability of the government to operate in a disaster scenario.
The rough last known location of American Airlines Flight 5342 before the crash
New US defence secretary Pete Hegseth revealed the Black Hawk crew’s training mission on Thursday, saying they “were on a routine, annual re-training of night flights on a standard corridor for a continuity of government mission”.
The army has come under scrutiny for flying at night near a busy airport, but officials pointed to the sensitive nature of the operation.
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“Some of their mission is to support the department of defence if something really bad happens in this area, and we need to move our senior leaders,” said Jonathan Koziol, the chief of staff of the army’s aviation directorate.
The most recent time the mission is known to have been carried out – for real – was on September 11, 2001, when a Black Hawk was sent to collect then deputy secretary of defence Paul Wolfowitz following the terror attacks on New York and Washington.